Synaesthesia in one language only

New Scientist have recently published a fascinating exchange on synaesthesia which has highlighted that some bilingual people with the condition experience the effect in one language only.

A reader wrote in to suggest that the consistently found associations of certain colours with specific letters of the alphabet may be due to with the way the letters are represented in children’s ‘ABC’ books.

Psychologist Dr Julia Simner replied, noting that research shows this wasn’t the case, but most interestingly, her letter indicates that some bilingual people only experience synaesthesia in one language:

Slessenger’s proposal that synaesthetes’ colours stem simply from childhood ABC books is sensible, but has been tested, and rejected, elsewhere. Anina Rich and colleagues traced 136 ABC books published as far back as 1862 – of which, surprisingly, only 38 used colour in any prominent sense. However, only 1 in 150 of their synaesthetes experienced colours consistent with any alphabet book [pdf].

Additionally, although Slessenger’s account is plausible for the examples he provided (eg, “A is for (red) apple, it’s less tenable when the entirety of alphabetic colours are considered. Indeed if synaesthetes’ colours were indicative solely of ABC learning, this would imply they lived in a world of green elephants (E), red mothers (M), black and blue tigers (T) and yellow cats (C).

Instead, our research indicates a different cause: synaesthetes colour their alphabets with a sophisticated, unconscious rule-system, in which, for example, associations are mapped according to the frequency with which letters and colour terms are encountered in the English language. High-frequency letters such as A are significantly likely to pair with high-frequency colour terms such as “red”.

Finally, Slessenger suggests our synaesthetes should be given symbols from an unknown language to test whether associations are independent of experience. This approach has been investigated and proved unhelpful. Strangely, depth of familiarity is not a strong predictor of synaesthetic colouring since some bilingual people have colour in only one language – and some monolinguals have colour for languages they do not understand.

In original letter was in response to a May article on the condition and some of Simner’s research findings. Unfortunately, the main article is behind a pay wall, but the letters are fascinating in themselves.